Source / episode info

• **Episode:**616
• **Title:**DIP Ep 616: USMLE Step 2/3 Rapid Review Series 127 (More Basic Sciences)
• **Published:**2025-07-28
• Source:Episode page

One-liner

Episode 616 provides a rapid review of high-yield basic sciences, emphasizing classic anatomical locations of pediatric brain tumors, detailed patterns of cranial nerve deficits (I-XII), differential diagnoses for pulmonary hypertension, and the pathophysiology of genetic syndromes like mitochondrial disorders and VACTERL.

High-yield summary

• Pediatric Brain Tumors: Know the "favorite spots": Cerebellum (Pilocytic Astrocytoma); Ventricles (Ependymoma); Meninges/Convexities (Meningioma); Corpus Callosum (Glioblastoma).
• Cranial Nerve Deficits: Lateral brainstem strokes affect sensory pathways (pain/temp) ipsilaterally; Medial brainstem strokes affect motor pathways and can cause contralateral corticospinal signs.
• Pulmonary Hypertension: Be able to differentiate causes: BMPR2 mutation (Idiopathic PAH); VSD -> Eisenmenger Syndrome; Scleroderma/CREA (Direct vasculopathy).
• Mitochondrial Disorders: These are inherited maternally, present with ragged red fibers on muscle biopsy, and often cause lactic acidosis due to reliance on anaerobic glycolysis.
• VACTERL Association: A constellation of congenital anomalies requiring screening for vertebral, anal, cardiac, tracheo-esophageal, renal, and limb defects (VACTERL).

Learning objectives

• Identify the anatomical predilection sites for common pediatric brain tumors (e.g., cerebellum, ventricles).
• Differentiate the clinical presentation and underlying pathology of various cranial nerve palsies based on their motor/sensory function and location (lateral vs. medial brainstem).
• Correlate systemic diseases (scleroderma, NF2) or drug exposures (nitrofurantoin, aminoglycosides) with specific organ damage (PH, CN VIII neuropathy).
• Understand the pathophysiology of mitochondrial disorders, including the mechanism leading to lactic acidosis.
• Recognize the key components and screening requirements for congenital syndromes like VACTERL and v.v.

Board exam buzzwords